Gas Spewing Out Main Tank...

[mlilly]

First of thank you ahead of time for any thoughts, I am not very mechanically inclined so all thoughts are very much appreciated...

I have a 1974 Bronco. I bought the truck a few months ago. I had a mechanic put a new aux tank on, which never seemed to be working correctly. So the other day I filled the main tank and then started filling the aux tank when all of the sudden gas started spewing out the main tank with the gas cap on? I thought the two tanks were not connected but for some reason they are impacting one another now? Also, the gas gauges are not working anymore...

Any thoughts on what might be happening? I live in the Northern CA so any recommendations for someone that I might be able to take a look would also o be appreciated.

Thank you

Mark

 

[tatersalad]

There should be a fuel selector switch under the drivers seat to keep them separate.. however you need to provide more details, like .. efi, carburated etc.. pictures of what the guy installed would help too.

 

[mlilly]

Thanks tatersalad...

It is a carburetor... It should matter which tank is chosen under my seat for filling the tanks, correct? it seems odd that when filling one tank, the other one starts overflowing even with the cap on?

I will have to take some photos in the morning, hopefully that will help a bit.

Thank you

Mark

 

[DirtDonk]

They would not normally have any way of being directly connected in the way of the filler tube or other large hose that could do that. But they are semi-interconnected via the evap system (charcoal canister) which has one plastic tank behind the driver's shoulder and a metal canister mounted to the frame rail at the back of the passenger side front wheel well.
But even that should not allow this to happen, unless it's somewhat plugged.

More often than not a full tank will expand when it gets got and spew out, but having it happen that quickly is stranger even than the normal tank filling issues these things have!

Not sure where to look next, but as said, pics would help. And check to see if the small vent hoses are connected and running up into the body on the driver's side rear wheel well. And for the metal can on the passenger side too.

For posting pics, you will have to use an online image hosting site, such as SuperMotors, or become a contributor for 12 bucks a year here. The only way to post images directly is to become a contributor. But you can link to photos on other sites and we'll still be able to see them.
Also, in lieu of spending money (even though that 12 bucks a year is a bargain for hanging out with all of us!%) ) you can use your "garage" function in your User CP and we can click on your garage link.

Also in a pinch you can send some pics to one of us with the yellow "contributor" beneath their username.

Any of the above can work.
Good luck.

Paul

 

[tatersalad]

Wo info on what your mechanic did it's going to be hard to figure out. Was the main tank full at the time you were filling the aux. tank? If so could have simply been coincidental from expansion on a warm day as Paul previously stated. I usually don't completely top off and I make sure I run on that tank a few miles to stop this. In my efi setup my aux. is used to transfer fuel and is tee'd into the return line. The intank pump would pull the fuel into the main w/o my knowledge until I put the selector valve back in to stop it.

 

[Broncobowsher]

Fuel tank venting. That is interconnected. My guess is the aux tank got full enough that you started filling the vent line. Guessing it is unhooked at the main tank. So the overflow off the aux tank you were filling was dumping at the main tank.

Do you still have the full emissions stuff hooked up? Evaporative side that is. Charcoal canister, the little plastic bottle behind the driver's side B-pillar. That stuff.

 

[sprdv1]

Sounds like some built up pressure

Make sure vented properly

 

[Chief Master Sergeant]

I was working in my shop yesterday and started smelling gas. The heat had caused the tank to pressurize and gas was coming out of the weakest link. Might be what was happening to you. I took the gas cap off and it vented quickly and the leak stopped.

 

[Timmy390]

Happens to me all the time.....the spewing that is.....well used to.

Cold gas from the underground tank at the station to 90 degree plus hot empty tank and no vent. Let it sit for a few and gas starts spewing. Something has to give when the cold gas starts expanding.

Make sure your main tank is correct for your year. Mine isn't. I replaced my leaking main tank with a used earlier non vented main tank and that's when my problems started. Traded rust for spewing....

I tend to keep this from happening by only filling the tank 3/4 full in the summer. Well really it's a habit now so year round. And don't park with the D-side downhill. If the tank is full gas blocks the filler neck and with no vent, pressure builds and....spew

Tim

 

[Rox Crusher]

In the summer I only fill mine full if I am going to drive it for a while, this way I don’t end up with expanding gas leaking everywhere